No Man Left Behind

You'll automatically accept this quest once you've used two tickets during the Summer Festival. To kick things off, head to the central station in Heimdallr. After a cutscene, make your way to the west side of Heimdallr Underground 3.

Boss: Regenenkopf Type-II
Here's a look at the boss's stats:

Enemy	HP	Slash	Thrust	Pierce	Strike	Elemental Efficacy	Item Drop
Regenenkopf Type-II	72765	☆☆	☆	☆☆	☆☆☆	E - 80, WA - 100, F - 160, WN - 120, TI - 100, SP - 80, MI - 140	Leg Breaker III

When the fight begins, use your Scan command to learn its weaknesses. Immediately activate the Brave Order Crimson Break and focus on getting the boss into its break status. Once broken, switch to the Brave Order Blast Force, use Spirit Unification, and then finish it off with your most powerful S-Crafts.

Before heading deeper into the underground, make sure you're prepared for the next few fights. On your way to Heimdallr Underground 2, take out any enemies you encounter until you've accumulated at least 200 CP and 5 BP. This will make the upcoming battles much smoother.

The strategy used for the Regenenkopf Type-II should also work well against the Supreme Giant Isopod, Dicephalosaurus, and Great Abyss that you'll encounter.

Continue progressing through Heimdallr Underground. After defeating the bosses, head to the west side of Heimdallr Underground 1. A new path will open up. Head south, then west to find a chest containing a Zeram Powder.

From there, go east of that intersection and continue south until you find another room with a chest. This one holds a Hyoushou Gem, which is great for boosting your EP and ATS.

Finally, make your way to the southwest part of the map to face the next boss.

Boss: Magic Knight Azura-Luciel
Here are the stats for this boss:

Enemy	HP	Slash	Thrust	Pierce	Strike	Elemental Efficacy	Item Drop
Magic Knight Azura-Luciel	123407	☆☆	☆☆	☆☆	☆☆	E - 100, WA - 150, F - 100, WN - 50, TI - 100, SP - 80, MI - 120	Mars Gem

Just like the previous boss, start by scanning Azura-Luciel. Activate Crimson Break and focus on breaking its guard. Once it's vulnerable, use the Brave Order Blast Force and unleash all your S-Crafts in rapid succession to defeat it.

After defeating Magic Knight Azura-Luciel, the quest will be completed. You'll receive another ticket and 6000 Mira as your reward.